This project is a simple adaptation of the classical Yamaha CS-80 synthesizer. Here we focus on the Voltage Controller Filter section of the CS-80. The original CS-80 has two State Variable Filters, one outputting low pass filter signal and the other outputting bandpass and high pass signals. Since a State Variable Filter can generate low pass, bandpass and high pass signals at the same time, we choose to build only one State Variable Filter. We also made modification over the feedback path of the State Variable Filter. Originally the feedback is controlled by an OTA. Now we simplify it to a pure resistive feedback path. By increasing the potentiometer value, the feedback resistance will increase and thus reduce the feedback and increase the resonance amount (or Q). Current generating circuit is based on a BJT pair. All circuit design and layout are being done in Eagle.